Nutrients, Sediments and Toxins

Many of the Bay’s problems are caused by what flows into it from its many tributaries. Nutrients are those substances that stimulate growth of plants and algae. When this happens excessively, and the tiny plants die in the water, their decay process uses up oxygen in the water. Other plants and animals are starved for oxygen, do not thrive, become more susceptible to disease, and often die. “Fish kills” occur when large numbers of fish die and float to the surface. The principal nutrients of concern are nitrogen and phosphorus that can come from agricultural sources, wastewater treatment plants, over-fertilized lawns, septic systems, runoff from urban streets and parking lots.

Sediment flows into the Bay at all times, but in huge quantities following rain events. Sediment clouds the water, coats the leaves of underwater plants and smothers shellfish on the bottom. Excess sediment washes off farm fields, construction sites, quarries and anywhere that the soil is disturbed.

Toxins come from a wide variety of sources, including industrial sites, agricultural and horticultural pesticides, household cleaners and disinfectants, pharmaceutical products, runoff from city streets and airborne discharges from coal-fired power plants. Many of these accumulate in the flesh of aquatic animals and may cause diseases or congenital malformations. The effects on humans are less well documented, but a cause for concern.